The conventional technique to generate polarized light generally directs a non-polarized light through a polarizer (or called polarization lens) which allows the light to pass through only in a single polarized direction and filter out light in other directions. The polarized light thus formed can be used as the light source of LCD panels or on various types of photoelectric elements.
While the aforesaid conventional technique can generate the polarized light, when in use on the LED panels or other photoelectric elements an extra polarizer has to be added. As a result, total thickness increases that makes diminishing the size and thickness of elements more difficult. Moreover, the polarizer usually is made from plastics and easily degraded and damaged by scraping. The optical lens formed with the polarizer also is more expensive. Light passing through the polarizer also generates a slight phase difference that creates troubles in optical design.
The conventional technique for making chips of blue and green LEDs (light emitting diodes) mainly adopts a MOCVD (Metal Organic Chemical Vapor Deposition) method on a sapphire substrate to grow LEDs containing multi quantum wells of GaN or AlInGaN to form an Epitaxial wafer, then is processed to become LED chips.
Shuji Nakamura et al. in Japan have reported that the polarization can occur in lattice plane of m-plane or A-plane in GaN or AlInGaN. The polarization ratio can be represented as follow:ρ=|Iperpendicular−Iparallel|/|Iperpendicular+Iparallel|
where I is light intensity, Iperpendicular is light intensity in vertical polarization direction, and Iparallel is light intensity in horizontal polarization direction.
However, it does not have much practical value since the polarization ratio ρ is very small (about 0.17). Hence, the present invention aims to provide a technique to improve the polarization ratio and a practical element manufacture process.